The objective of this proposal is to develop a quantitative understanding of the relationship between membrane ionic fluxes and electrical events in vascular smooth muscle from the amphibian, Amphiuma. A multidiciplinary approach will be used. Transmembrane fluxes of Na+, K+ and Cl- will be studied in order to evaluate the relative permeability of the membrane to each ion. The normal cellular content and concentration of the relative importance of each ion to the resting membrane potential. Membrane electrical parameters will be examined by use of conventional bridge techniques. In addition, single microelectrode current- and voltage-clamp experiments will be performed to further elucidate the ionic basis of the electrical events. Electron microscopic morphometry on whole tissue strips will be directed toward evaluation of the cellular to extracellular space ratio, and of the volume to surface area ratio of the cells. This latter datum is important in calculation of both the ionic permeabilities and electrical parameters such as specific membrane resistance. These experiments will be conducted both in vascular strips, and in preparations of disaggregated cells. Experimentation on single cells, or suspensions of isolated cells is expected to alleviate some of the difficulties associated with intact tissue preparations. Studies on tissue strips should aid in the evaluation of the single-cell work, and should facilitate comparison of the data with the large body of whole-tissue studies already available. There is evidence that some vascular diseases are manifested as alterations in vascular smooth muscle membrane function. It is expected that this study will contribute to understanding of basic membrane physiological processes of vascular smooth muscle in health and disease.